In a conventional lithographic printing press, ink or an ink emulsion is supplied to a drum using a print unit. As is known, the ink is typically ultimately transferred to a plate cylinder via a number of intermediate drums or cylinders. As shown in FIG. 1, a typical print unit 10 can include a page pack 12 and an ink rail assembly 14. The page pack 12 includes an ink inlet 16, a pump 18, and a control valve 20. The page pack 12 pumps the ink through a plurality of supply lines 22 under pressure to the ink rail assembly 14, which is mounted closely adjacent to a drum 24. Each of the supply lines 22 is typically a length of tubing or flexible hose. The ink rail assembly 14 typically includes an ink rail 26 having a number of orifices 28. The orifices 28 are spread out along the length of the ink rail 26 and are adapted to deliver ink to the drum 24. Thus, ink is pumped from the page pack 12 through a length of supply line 22 to the ink rail 26 and through the orifices 28, such that the ink is applied directly to the surface of the drum 24.
In a conventional printing press there are typically a number of print units. Further, there are typically two drums for each print unit with at least one ink rail assembly for each drum. Thus, the ink may be supplied to each of the ink rail assembly through a system of supply lines and/or headers.
Such a conventional arrangement may have a number of disadvantages. Some of these disadvantages may include, for example, that it is difficult to switch web sizes without having to replace the entire ink rail. Further, on a conventional system it is very difficult to purge the ink from the system due to the length of the supply lines, making color changeovers more costly due to increased purge time and wasted ink that is stored in the lengthy supply system. Finally, on a conventional arrangement there is much duplication of hardware, such as multiple hose assemblies and multiple sets of mounting systems.